A nearly 2-fold increase was seen in the rate of Alzheimer disease diagnoses among men with prostate cancer who were treated with androgen deprivation therapy (ADT), according to a review of the electronic medical records of thousands of patients at two major medical institutions. The study, published in the Journal of Clinical Oncology (10.1200/JCO.2015.63.6266), demonstrates emerging techniques for extracting biomedical data from ordinary patient medical records.

Testosterone can promote the growth of prostate tumors, therefore ADT has been used to lower testosterone and other androgens in patients with prostate cancer since the 1940s. In the United States, approximately one-half million men currently receive ADT as a treatment for prostate cancer.

The researchers scanned the records of approximately 5.5 million patients from two hospitals: Stanford Health Care, in Palo Alto, California, and Mount Sinai Hospital, in New York City. Among this cohort, they identified 16 888 patients with nonmetastatic prostate cancer, 2397 of whom were treated with androgen deprivation therapy.

Rate of Alzheimer disease diagnoses was an estimated 1.88 times higher among patients who were treated with ADT in a median follow-up period of 2.7 years compared with those patients who did not receive ADT, the study found. The subset of men treated with ADT for more than 12 months had a 2.12 higher risk, more than double that of patients with prostate cancer who were not treated with ADT.

Senior author Nigam Shah, MBBS, PhD, associate professor of biomedical informatics research at Stanford said the idea for the study started with lead author Kevin Nead, MD, who is now a resident at the University of Pennsylvania in Philadelphia. Nead noticed references in the medical literature to subsequent cognitive declines in men who received ADT treatment for prostate cancer.

"There was some chatter in the literature," said Shah. But no one had formally tried to find out if ADT therapy leads to cognitive defects.

"This is the kind of question that typically you would need a large clinical trial to answer," said Shah. But a formal clinical trial would be enormously expensive. "So instead, we're making secondary use of existing clinical data collected as part of routine medical care."

Although ADT may increase the risk of defects in cognition and hand-eye coordination for reasons other than Alzheimer disease, the team decided to focus specifically on Alzheimer because the condition is easier to identify in medical records, said Shah. "Broader dementias and vascular dementia are kind of hard to quantify and define, so we had to narrow the scope of the analysis to make it feasible with the methods that we have available," he said.

Patients receiving ADT who are concerned about the potential risks should discuss their concerns with their physicians. "The association found in this study should be evaluated in the context of the overall treatment choices available to any specific patient," Shah said. "This study demonstrates the value of using existing EMR data to quantify the trade-offs that various treatments offer."